BORÉALES ENERGY is bringing to market innovative energy storage systems, notably its compact energy storage unit, coupled with a full range of services.

Our Modular Static Thermodynamic Electricity Storage solution (Stockage Thermodynamique d’Électricité Modulaire et Statique or STEMS) allows Boréales Energy to provide unrivalled performance, ease of installation, flexibility, and TCO.

Designed to be installed on the low-voltage grid, our STEMS units bring down energy storage costs and provide a wide range of services for electricity grid players (including end of line frequency balance).

Unrivalled performance, ease of installation, flexibility, and TCO.

The STEMS unit comprises two standard containers stacked one on top of the other:

STEMS unit characteristics:

  • Dimensions: 12 × 2.5 × 5 m (w × l × h);
  • Electrical power: 100 kW;
  • Stored energy: 800 kWh.

STEMS units can be made available to grid managers and instantly activated remotely as required for load balancing:

  • Grid electricity consumption (compressor startup)
  • Grid load balancing (compressor shutdown)
  • Electricity production (turbine startup)


The Modular Static Thermodynamic Electricity Storage system operates by storing energy thermally. More specifically, STEMS combines two thermodynamic cycles, leveraging the energy storage properties of two Phase Change Materials (PCMs): pure water (hot source, phase change at 0 °C) and a salt solution (cold source, phase change at −50 °C).

The diagram below gives an overview of how the STEMS unit works during energy loading, storage, and release:

The STEMS unit uses electricity to freeze brine, using the refrigeration cycle.

The brine remains frozen throughout the storage period. The outstanding performance of the STEMS unit means that only a very small amount of the stored energy is lost during this phase.

The STEMS unit produces electricity by liquefying the frozen brine, using the Organic Rankine Cycle (ORC).

Technology used:
STEMS uses a number of mature thermodynamic technology building blocks to perform the phases outlined above:

· Compressors;
· Pumps / expansion valves;
· Turbines;
· Exchangers;
· Static Thermal Accumulator (Accumulateur Thermique Statique, or ATS).

STEMS is thus based on proven technologies. At the same time, the Boréales Energy offering is based on a unique intellectual property (IP) rights portfolio focusing on thermodynamic technology.

Innovative technology

The way these technologies are integrated is unique, allowing Boréales Energy to provide far better performance, ease of installation, flexibility, and TCO than our competitors.

A number of solutions use thermal energy storage based on a phase change material. However, none of these solutions leverages the full potential of thermal storage using water phase change. This is because doing so requires the accumulator to be incorporated in the primary refrigeration loop, without any intermediate exchanger or fluid.

To date, no such accumulator exists.

The innovative nature of Boréales Energy technology resides in the development of a complete system incorporating a revolutionary exchanger that can be integrated into both the refrigeration cycle and the Organic Rankine Cycle.

Its exchange surface is very large, resulting in a very small pinch, so the exchanger can improve the round trip efficiency of the entire electricity storage system.